Electric fish shocking devices find numerous applications in stunning and collecting fish. Electric fish shocking devices also have applications in electric fish barrier arrays and electric fish guidance systems. For a description of such a fish barrier, see U.S. Pat. No. 4,750,451 issued on Jun.14, 1988 to David V. Smith.
Fish shocking devices typically seek to minimize the harm done to fish while accomplishing their designed functions. For example, electrofishers induce the fish to swim toward the anode (galvanotaxis) and hold the fish in an immobile state (galvanonarcosis) so they can be collected without excessive harm or damage. In electric fish barriers, the fish must be prevented from crossing the barrier without being injured or killed in the process.
In order to maximize the effectiveness of the device, a careful balance must be maintained between applying the needed electrical power and minimizing fish damage. This is particularly true with threatened or endangered fish species. Factors that affect the amount of electrical power needed include: Voltage level, Constant versus Varying or Pulsed Current, Direct Current (DC) versus Alternating Current (AC), the conductivity of the water, the fish species, and fish size.
Prior art electric fish shocking devices generally limit the adjustment of waveform parameters and usually only provide a small number of simple waveforms. Typically, prior art electric fish shocking devices employ a series of rectangular pulses, and permit the user to manually adjust the voltage, width and frequency over narrow ranges.
In addition, prior art electric fishing devices usually have not provided flexibility for automatically adjusting these parameters as conditions change, and have been ill-equipped to generate a variety of other waveform types that might prove more effective or less harmful to the fish in given circumstances. Thus, there is a need for a new and improved electric fish shocking device which overcomes such difficulties.
In accordance with the present invention, this need is fulfilled by placing the waveform generating burden on programmable hardware. In a preferred embodiment, a microprocessor controls a high speed switch which is used to control the output of a high voltage power supply. Thus, the device has the ability to produce continuous output or variable length pulses. The programmable hardware allows the generation of more complex waveforms such as gated bursts (a number of short pulses followed by a longer quiet period) and pulses that vary their width and/or frequency over time (Pulse Width and/or Frequency Modulation).
If provision is made for programmable control of the power supply output voltage level, then the hardware can produce amplitude modulated waveforms. If environmental feedback sensors are used, such as water conductivity monitors or sonar fish locators, then the output waveform parameters can automatically adjust to optimize the desired effect while minimizing any harm done to the fish.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.